Mast Cell-Dependent Contraction of Human Airway Smooth Muscle Cell-Containing Collagen Gels: Influence of Cytokines, Matrix Metalloproteases, and Serine Proteases

Abstract

In asthma, mast cells infiltrate the airway smooth muscle cell layer and secrete proinflammatory and profibrotic agents that contribute to airway remodeling. To study the effects of mast cell activation on smooth muscle cell-dependent matrix contraction, we developed coculture systems of human airway smooth muscle cells (HASM) with primary human mast cells derived from circulating progenitors or with the HMC-1 human mast cell line. Activation of primary human mast cells by IgE receptor cross-linking or activation of HMC-1 cells with C5a stimulated contraction of HASM-embedded collagen gels. Contractile activity could be transferred with conditioned medium from activated mast cells, implicating involvement of soluble factors. Cytokines and proteases are among the agents released by activated mast cells that may promote a contractile response. Both IL-13 and IL-6 enhanced contraction in this model and the activity of IL-13 was ablated under conditions leading to expression of the inhibitory receptor IL-13Rα2 on HASM. In addition to cytokines, matrix metalloproteinases (MMPs), and serine proteases induced matrix contraction. Inhibitor studies suggested that, although IL-13 could contribute to contraction driven by mast cell activation, MMPs were critical mediators of the response. Both MMP-1 and MMP-2 were strongly expressed in this system. Serine proteases also contributed to contraction induced by mast cell-activating agents and IL-13, most likely by mediating the proteolytic activation of MMPs. Hypercontractility is a hallmark of smooth muscle cells in the asthmatic lung. Our findings define novel mechanisms whereby mast cells may modulate HASM-driven contractile responses.

Mast cell-orchestrated immunity to pathogens

“…For example, mast cells can influence the behaviour of nerve cells, the first cell type recognized as a target of mast cell signals, through products such as histamine (and serotonin in the case of mouse mast cells) 27 . Mast cells also communicate with smooth muscle cells 63 . Together, these interactions could potentially promote the elimination of pathogens from the body, such as that which occurs during mast cell-promoted expulsion of bacteria and fluids from the gut in response to cholera and clostridium toxins 64,65 .…”

Mast cell proteases: multifaceted regulators of inflammatory disease

“…It has also been shown that MC proteases can activate yet other MMPs. [80][81][82] Potentially, MC protease-mediated ECM modification could lead to a more efficient influx of inflammatory cells into the tissue and to effects on cellular adhesion to the ECM. It is also noteworthy that degradation of the ECM can unleash proinflammatory cleavage products, such as fibronectin fragments or chemokines/growth factor bound to proteoglycans present in the ECM.…”

IL-33 synergizes with IgE-dependent and IgE-independent agents to promote mast cell and basophil activation

“…Quantitation from densitometric analysis for phospho-protein signals was normalized by cell numbers seeded. Fold change over control conditions is indicated for representative experiments as stated in the ''Materials and methods'' section (HFL-1) [41] or human airway smooth muscle cells (HASM) [48], as a model for remodeling changes associated with asthma. To examine functional consequences of the synergistic activation of HMC-1 by IL-33 and SCF, HMC-1 cells were co-embedded in collagen gels with either HFL-1 or HASM, and contractile responses were measured as a decrease in gel surface area.…”